Curved tube structure and die for forming curved tube

Abstract

A curved tube structure, including: a tube main body including a bent portion at one portion in an axis line direction; and an enlarged cross-section portion formed along the axis line direction of the tube main body in an inner periphery inside a bending direction of the bent portion for enlarging a cross-section area of the tube main body.

What is claimed is: 
     
       1. A curved tube structure, comprising:
 a tube main body made of resin and including a bent portion at one portion in an axis line direction to be bent in a bending direction; and 
 an enlarged cross-section portion formed along the axis line direction of the tube main body on an inner periphery of the bent portion at only an inner side of the bent portion relative to the bending direction for enlarging a cross-section area of the tube main body, 
 wherein the enlarged cross-section portion has a concave portion protruding toward an outer peripheral side of the tube main body when the enlarged cross-section portion is viewed from the axis line direction, 
 the concave portion includes a bottom face and two side wall portions smoothly connected to the bottom face at two sides of the bottom face to form an arc when the enlarged cross-section portion is viewed from the axis line direction, and the two side wall portions are arranged apart from each other to form a distance therebetween, and 
 when the bent portion is viewed from the axis line direction, the distance between the two side wall portions is shorter than an inner diameter of the tube main body parallel to a measured distance between the two side wall portions and orthogonal to an axis line of the tube main body. 
 
     
     
       2. A curved tube structure according to  claim 1 , wherein the concave portion has a shape in which the two side wall portions and the bottom face protrude to the outer peripheral side of the tube main body to form the arc when the enlarged cross-section portion is viewed from the axis line direction. 
     
     
       3. A curved tube structure according to  claim 2 , wherein a border between each of the two side wall portions and the bottom face is bent to form the arc. 
     
     
       4. A curved tube structure according to  claim 1 , wherein the concave portion has a shape in which the two side wall portions have straight lines and the bottom face protrudes to the outer peripheral side of the tube main body to form the arc when the enlarged cross-section portion is viewed from the axis line direction. 
     
     
       5. A curved tube structure according to  claim 1 , wherein the concave portion has a shape in which the two side wall portions and the bottom face have straight lines. 
     
     
       6. A curved tube structure according to  claim 1 , wherein the bottom face of the concave portion forms a curved face protruding outwardly in the axis line direction when the concave portion is viewed from a side orthogonal to the axis line direction. 
     
     
       7. A curved tube structure according to  claim 1 , wherein the bottom face of the concave portion forms an inclined face when the concave portion is viewed from a side orthogonal to the axis line direction. 
     
     
       8. A curved tube structure according to  claim 1 , wherein the concave portion is formed only at the inner side of the bent portion relative to the bending direction, and
 the bottom face and the two side wall portions are integrally connected to form the arc having a curvature larger than that of an inner periphery of the tube main body. 
 
     
     
       9. A curved tube structure according to  claim 1 , wherein the tube main body has a flow path having a circular cross section, the bent portion has a further flow path communicating with the flow path and having an oblong cross section, and the concave portion is formed at a lower portion of the bent portion forming the oblong cross section. 
     
     
       10. A curved tube structure according to  claim 1 , wherein when the bent portion is viewed from the axis line direction, a distance between the axis line and the bottom face is longer than a distance between the axis line and the inner periphery at an outer side of the bent portion opposite to the bottom face, in a direction orthogonal to the axis line, so that the concave portion protrudes toward the outer peripheral side at the inner side of the bent portion further than the inner peripheral of the bent portion at the outer side of the bent portion. 
     
     
       11. A curved tube structure, comprising:
 a tube main body made of resin and including a bent portion at one portion in an axis line direction to be bent in a bending direction; and 
 an enlarged cross-section portion formed along the axis line direction of the tube main body on an inner periphery of the bent portion at only an inner side of the bent portion relative to the bending direction for enlarging a cross-section area of the tube main body, 
 wherein the enlarged cross-section portion has a concave portion protruding toward an outer peripheral side of the tube main body when the enlarged cross-section portion is viewed from the axis line direction, 
 the concave portion includes a bottom face and two side wall portions connected to the bottom face at two sides of the bottom face when the enlarged cross-section portion is viewed from the axis line direction, and the two side wall portions are arranged apart from each other to form a distance therebetween, 
 when the bent portion is viewed from the axis line direction, the distance between the two side wall portions is shorter than an inner diameter of the tube main body parallel to a measured distance between the two side wall portions and orthogonal to an axis line of the tube main body, and 
 the two side wall portions extend linearly toward the bottom face in a direction apart from the axis line, and the bottom face linearly extends between lower ends of the two side wall portions in a direction orthogonal to the axis line.